Temporal evaluation of a woodrat (genus Neotoma) hybrid zone based on genotypic and georeferenced data

Mauldin et al. (2014) examined 103 woodrats collected in 1988 from a putative contact zone located in Major County, Oklahoma, and provided evidence for a substantial level of hybridization between Neotoma floridana and N. micropus. This site was resampled in 2010, with 42 woodrats collected, and again in 2011, when an additional 88 woodrats were collected from 11 localities along a transect extending northwest to southeast of the center of the hybrid zone. These specimens were examined to: 1) serve as independent data sets, separated by 22 years, for a temporal comparison of hybrid zone characteristics and 2) determine the geographic extent of genetic introgression between the two species. All individuals were genotyped at 11 genetic markers (eight microsatellite loci, one mitochondrial gene-Cytochrome b, and two nuclear introns-intron 2 of the vertebrate alcohol dehydrogenase gene and intron 7 of the beta-fibrinogen gene) that were shown to be informative in the original study. Levels of allelic introgression were assessed at 12 localities (11 new localities, as well as the previously sampled putative contact zone) to determine size and continuity of the hybrid zone. Expanded geographic sampling revealed evidence of genetic introgression at 11 of 12 localities, although only two localities were determined to be active areas of hybridization in 2011. The temporal comparison revealed that characteristics of the hybrid zone (i.e., frequency of hybridization, directionality, location of the zone, and ratios of hybrid classes) remained similar between sampling events. These findings suggest hybridization between these species is ongoing but is intermittent and potentially ephemeral in this region.

Automated summary

The study provides evidence of ongoing but intermittent hybridization between Neotoma floridana and N. micropus in Major County, Oklahoma. Genetic analysis of woodrats collected at multiple localities over time showed evidence of genetic introgression at most sites, with only a few being identified as active areas of hybridization in 2011. The characteristics of the hybrid zone remained similar between sampling events, suggesting that hybridization between these species is ongoing but potentially ephemeral in this region.